Combine duplicated columns within a DataFrame

Question

If I have a dataframe that has columns that include the same name, is there a way to combine the columns that have the same name with some sort of function (i.e. sum)?

Answer 1

I believe this does what you are after:

df.groupby(lambda x:x, axis=1).sum()

Alternatively, between 3% and 15% faster depending on the length of the df:

df.groupby(df.columns, axis=1).sum()

EDIT: To extend this beyond sums, use .agg() (short for .aggregate()):

df.groupby(df.columns, axis=1).agg(numpy.max)